N-Hydroxy-4-(4-chlorophenyl)thiazole-2(3H)-thione as a Photochemical Hydroxyl-radical Source: Photochemistry and Oxidative Damage of DNA (Strand Breaks) and 2′-Deoxyguanosine (8-oxodG Formation)¶
作者:Waldemar Adam、Jens Hartung、Hideki Okamoto、Chantu R. Saha-Möller、Kristina Špehar
DOI:10.1562/0031-8655(2000)072<0619:nhctht>2.0.co;2
日期:——
On irradiation of N-hydroxythiazole-2(3H)-thione 3 at 300 nm, the photoproducts disulfide 4, bisthiazole 5 and thiazole 6 are formed. During this photolysis, hydroxyl radicals are released, which have been detected by spin trapping with 5,5-dimethyl-1-pyrroline N-oxide (DMPO), coupled with electron paramagnetic resonance spectroscopy. In the presence of supercoiled pBR322 DNA, irradiation of thiazolethione 3 induces strand breaks through the photogenerated hydroxyl-radicals, as confirmed by control experiment with the hydroxyl-radical scavenger isopropanol, Singlet oxygen appears not to be Involved, as attested by the lack of a D2O isotope effect. During the photoreaction of thiazolethione 3 in the presence of 2'-deoxyguanosine (dG), the latter is photooxidized (ca 10% conversion after 2 h of irradiation) to the 7,8-dihydro-8-oxo-2'-deoxyguanosine as the main oxidation product. The dG conversion levels off after complete consumption of thiazolethione 3 and is suppressed by the addition of the hydroxyl-radical scavenger 2,6-di-tert-butyleresol or DMPO, Since the photoproducts 4-6 are ineffective as sensitizers for the photooxidation of dG and DNA, the hydroxyl radicals released in the photolysis of thiazolethione 3 are the oxidizing species of DNA and dG, These results suggest that the thiazolethione 3 may serve as a novel and effective photochemical hydroxyl-radical source for photobiological studies.